Atreyu’s a great choice. I like The Neverending [name_u]Story[/name_u] association a lot, as well of the quirkiness of the name in general.
Atreyu Brynjar / Atreyu [name_m]Vidar[/name_m] (the old Norse name element arr means ‘warrior’)
Atreyu [name_m]Forrest[/name_m] (mentioned already, but I like this one)
Atreyu [name_m]Heron[/name_m] (derived from Greek hero, meaning ‘hero/warrior’) / Atreyu [name_m]Theron[/name_m]
Atreyu [name_m]Thorn[/name_m]/e
Atreyu [name_m]Caspar[/name_m]
Atreyu [name_m]Peregrine[/name_m]
Atreyu [name_m]Silas[/name_m]
Atreyu [name_m]Wolf[/name_m]
Atreyu [name_u]Ash[/name_u] (I like the alliteration here - another nod to The Neverending [name_u]Story[/name_u] perhaps, with the main character’s BBB)